Decoration devices may be used to enhance the appearance of a room or an object or to provide entertainment. For example, some decoration devices may be in the form ornaments that are hung from a wall, a mantle, or a tree so as to enhance the overall decorative appearance of that wall, mantle, or tree. In another example, a decoration device may be adapted to rest upon a tabletop or other surface and may provide entertainment for those viewing the device.
In some circumstances, decoration devices may include motion, colors, shapes, or lights to provide a appearance that is associated with a particular season, holiday, event, or theme. A powered ornament device may include at least one component that is movable relative to another component. For example, a traditional children's music box may include a figurine (e.g., a dancer) that rotates relative to a stationary base as a musical sound is emitted from the box.
Electrically powered, movable ornaments and other such decoration devices typically include an AC motor to drive the motion of the movable component. Such AC motors are typically driven off 120 V alternating current which is readily available in residential environments. The AC motors generally rotate at set rotational speed for a given load. That rotational speed often significantly exceeds that desired for ornament applications, so the AC motor output shafts have been coupled to gearbox in order to reduce the speed. With a decrease in shaft speed comes an increase in torque and this increased torque is usually substantially more than that required to drive the frictional and inertial loads in a typical ornament application.
Pulse-width modulation (PWM) controllers may be used in lieu of gearing to control motor speed, but PWM techniques have generally been considered unacceptable for ornament applications because the throttling necessary to achieve the appropriate shaft speed generally yields a torque that is insufficient to drive the ornament or to drive the ornament smoothly given variations in drive line friction. Moreover, use of PWM controlled motors would substantially increase manufacturing costs due to the combined cost of the PWM microcontrollers and the complex gear systems that would have be used to account for the low torque output of PWM controlled DC motors. For both of these reasons, AC motors with reduction gearing have been used in lieu of PWM controlled motors in ornament applications.